Bone fractures are a very common orthopedic injury resulting from trauma and sudden loads or stresses applied to bones or a result from bones being weakened by certain diseases. More than 250,000 femur fracture patients are seen per year in the U.S. on average. Bone fractures are either a complete or partial break in a bone and in some cases a simple cast to immobilize the injury site is not enough to completely heal the fracture. Immobilization from casts may not be enough to completely heal the fracture if a malunion (when both ends of the fractured bone misalign) occurs and/or if a non-union (when the fracture gap is too large and the fractured ends cannot re-attach to one another) occurs. In the case of a malunion or non-union, a possible solution to the problem is by surgically inserting an intramedullary rod into the center canal (diaphysial) region of the injured bone and fixating it into place with screws. 

1. Proximal Femoral
Nail
BY ALEX BERTINO, COREY VAN DE HAY, ANDREW HNAT
ACA ENGINEERING
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2. Background
▶ Designed for femur injuries
▶ Largest and strongest bone
▶ Causes of injury
▶ Automobile accidents
▶ Falling
▶ Description of Fracture
▶ Location
▶ Pattern
▶ Skin condition
▶ Treatment based on type of fracture
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3. Medical
Need
▶ More than 250,000
patients per year
▶ Cast insufficient in
certain cases
▶ Malunion
▶ Non-union
▶ Necessitates usage of
intramedullary rod
Malunion Non-union
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4. Predicate Device
▶ Device Approval Date
▶ January 1997
▶ Product Code: JDS
▶ No recalls for this device in particular
▶ 10 recalls since 1995 for all JDS devices
▶ Standard Length PFN
▶ Synthes offers two options for PFN length
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5. The Device
▶ Components
▶ Nail
▶ Screws (2 Self-Tapping, 1 Locking)
▶ Threaded End Cap
▶ Material
▶ Titanium Alloy, Ti-6Al-4V(Nb)
▶ Intended use
▶ Indefinite Fixation within Intramedullary Canal
▶ Stabilization and Bone Integration
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6. Design and
Assumptions
▶ Anatomical geometry
▶ Biocompatible material
▶ Load transfer
▶ Restrict Stress Shielding
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7. Finite Element
Analysis
▶ Force: 6267 N
▶ Tripping
▶ Average male over 20 years
▶ Applied to the top of the rod
▶ Fixed at each screw hole
▶ Multiple Simulations
▶ Normal
▶ Bending
▶ Torsion
▶ Buckling/Frequency
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8. FEA Analysis:
Normal Force
▶ Order of magnitude lower
than yield stress
▶ Stress singularity at hole
▶ Caused by boundary
condition
▶ Not physically accurate
▶ Stress too low to cause
fatigue damage
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9. FEA Analysis:
Bending
▶ Tighter stress distribution
▶ Excessive stress at hole
▶ Singularity
▶ Not physically accurate
▶ Peak Stress half of yield stress
▶ System will not fail under
these conditions
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10. FEA Analysis:
Torsion
▶ Tightest stress distribution
▶ Excessive stress at hole
▶ Singularity
▶ Not physically
accurate
▶ Peak Stress slightly lower
than bending
▶ System will not fail under
these conditions
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11. FEA Analysis:
Buckling/Frequency
▶ Critical load factor: 183.7
▶ Minimum resonance
frequency: 2071.6 Hz
▶ System will not fail due to
Buckling/Frequency
Buckling Frequency
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12. Manufacturing and
Sterilization
▶ Wet (steam) autoclave sterilization
▶ Implanted medium to long-term device
▶ Sterilization level: 10-6 SAL
▶ Titanium casting to account for semi-
complex geometry
▶ Initial barrier costs high, but long-term
production will prove economical
Casting
Steam Autoclave
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13. Verification and Validation
▶ 510(k) Submission
▶ Substantial equivalence approach
▶ Predicate device
▶ Synthes PFN (Femur Intramedullary Rod
and Screws) - Std. Length
▶ Device Testing
▶ Static 4-point bending
▶ Static Buckling
▶ Static torsional
▶ Fatigue bending
Static Bending, Buckling, & Torsion Testing
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14. Conclusion
▶ Fills a medical need
▶ Large market for femur
implants
▶ Cost-effective to mass
produce
▶ FEA analysis yielded positive
results
▶ Further testing needed
▶ Positive outlook based on
current results
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15. References
▶ https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpmn/pmn.
cfm?ID=K970097
▶ https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfPCD/classi
fication.cfm?ID=JDW
▶ https://www.accessdata.fda.gov/cdrh_docs/pdf/K970097.pdf
▶ https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfTPLC/tplc.
cfm?ID=4455&min_report_year=1995
▶ https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfTPLC/tplc.
cfm?ID=4453&min_report_year=1995
▶ http://synthes.vo.llnwd.net/o16/LLNWMB8/INT%20Mobile/Synthes%2
0International/Product%20Support%20Material/legacy_Synthes_PD
F/DSEM-TRM-0714-0122-1_LR.pdf
▶ https://en.wikipedia.org/wiki/Femur
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16. References
▶ http://52.62.202.235/sites/default/files/TDwyer/Tibial%20Hypertrophic%20
Nonunion%20.jpg
▶ http://www.afrjpaedsurg.org/articles/2011/8/1/images/AfrJPaediatrSurg_2
011_8_1_34_78666_f2.jpg
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